July 9 (Bloomberg) -- Mutations within a small cluster of
genes tied to tumor growth are involved in three-quarters of the
cases of the most common form of lung cancer, according to a
study that could help link treatment to specific genetic flaws.

The research is the most comprehensive genomic analysis of
adenocarcinoma, a cancer that forms in the tissues near the
outer parts of the lungs and is usually linked to smoking,
though it can occur in nonsmokers. Researchers identified 18 key
mutations in an examination of 230 adenocarcinoma lung tumors,
according to the study published today in the journal Nature.

The finding adds to the range of genetic alterations known
to be involved in lung cancer. In addition to leading to new
drugs against new tumor targets, it may also help identify more
patients who can be treated with cancer medicines already on the
market that target specific growth-promoting proteins.

“To treat lung cancer you are not going to have a silver
bullet, you are going to need a lot of different combinations of
treatments against different targets,” said Matthew Meyerson, a
professor of pathology at Harvard Medical School and a lead
investigator on the study.

In particular, more than three-quarters of patients had
changes in a cluster of related genes called the RTK/RAS/RAF
pathway. Mutations in this group of genes can cause growth
signals to become stuck in the on position, promoting runaway
tumor expansion.

While the signaling pathway has long been known to be
involved in lung cancer, the study found additional types of
mutations in the pathway. Some patients have mutations in a gene
called RIT1 that was not known to be altered in lung cancer,
according to the research.

Xalkori Target

The study also confirmed and solidified previous findings
that some lung tumors have abnormalities in a gene called MET,
said Meyerson, who is also at the Broad Institute in Cambridge
and the Dana-Farber Cancer Institute. That suggests that Xalkori
from Pfizer Inc., a drug already approved for treating lung
cancer patients with an abnormality in a gene called ALK, might
also help in patients with MET alterations, Meyerson said.

The lung cancer data are part of a broader project by the
National Institutes of Health called the Cancer Genome Atlas,
which is analyzing samples from numerous types of malignancies.
In 2012, the project’s researchers had examined another less
common type of lung cancer, squamous cell, and found mutations
in 11 genes from 178 tumors they sequenced.